The instant invention relates to systems for deploying gas-operated vehicle occupant safety restraints, such as vehicle air bags, which seek to optimize occupant protection notwithstanding variations in occupant size and/or position within the vehicle at the time at which safety restraint deployment is otherwise deemed advisable.
The prior art teaches inflation systems for deploying an air bag in a motor vehicle which typically include a single gas generator in fluid communication with the interior of the uninflated air bag. In the typical embodiment, the gas generator is triggered by an air bag firing circuit when the sensed vehicle acceleration exceeds a predetermined threshold value, as through the use of an acceleration-responsive inertial switch and an explosive "squib."
In a variation upon this design, U.S. Pat. No. 4,928,991 to Thorn teaches an aspirating inflator assembly for a vehicle occupant restraint which employs a plurality of low cost gas generators to achieve an increased aspiration ratio. Each of Thorn's identical gas generators has an identical output characteristic, i.e., generate a like quantity of gas effluent over a like amount of time; and the basic manner in which each gas generator is triggered remains the same, i.e., a "fire" signal for each gas generator is itself generated when the sensed acceleration exceeds a predetermined threshold value, thereby identifying the time at which each gas generator is to be triggered (sometimes referred to as its "actual time-to-fire" or "actual TTF"). Thorn further suggests that the use of multiple gas generators permits the adapting of the inflator assembly output characteristic to the conditions of the crash, i.e., vehicle velocity, ambient temperature, occupant size and/or position or other condition, presumably based upon values therefor as measured at the time that the "fire" signal is generated, by triggering the ignition of only some of the inflator assembly's multiple gas generators. Stated another way, under Thorn, a fire signal is generated by the firing circuit based solely upon received vehicle acceleration information, at which time the initiation of each gas generator is selectively triggered to provide a plurality of inflator responses.
In U.S. Pat. No. 5,074,583, Fujita et al teach an air bag system for an automobile which employs acceleration data to detect a vehicle collision or marked deceleration requiring deployment of the air bag. The system further controls when and how quickly to inflate the air bag upon such detection of a vehicle collision or marked deceleration based on occupant position as it is indirectly garnered from the occupant's "seating condition," i.e., the longitudinal position of the seat within the vehicle, the reclining angle of the seat back, pressure sensors in the seat and seat back, etc. Thus, as under the above Thorn patent, under Fujita et al, once a "fire" signal is generated by the system's firing circuit, the system attempts to further adjust the nature of the response, i.e., the manner in which the air bag is actually inflated, in response to indirectly-sensed occupant position data. There is no attempt to adjust the actual TTF, i.e., the time at which the "fire" signal is itself generated, based on the nature or severity of the crash experienced by the vehicle. Nor do Fujita et al attempt to further correlate or otherwise qualify system response with the nature or severity of the crash and, hence, system response under Fujita et al fails to differentiate, for example, between a short-period, high-velocity crash and a long-period, low velocity crash (each of which requires substantively different inflator response, notwithstanding an identical relative occupant position within the vehicle).